Method for in-situ utilization of fuels by combustion



y 1953 G. J. w. SALOMONSSON 2,841,375

METHOD FOR IN-SITU UTILIZATION OF FUELS BY COMBUSTION Filed March 5, 1954 2 Sheets-Sheet 1 FIG.1 H

?'?9 i l!!!. I 1 I I I I I c a|lc o 0095A ill! 4 OVERBURDEN \,E g f j FUEL CONTAINING LAyERS F ENZENTOR F102 AT TORNEY July 1, 1958 G. J. w. sssssssss ON 2,841,375

- METHOD FOR IN-SITU UTILIZATION OF Fi l e d M a r c h 5 l 9 54 I A L- ATTORNEY United States Patent METHOD FOR lN-SITU UTILIZATION OF FUELS BY COMBUSTIDN Application March 3, 1954, Serial No. 413,904

' Claims. c1. 262-3) This invention relates to methods for in situ utilization of carbonaceous deposits capable of combustion with combustion supporting gases to produce heat utilizable economically for heat treatments both above and below ground particularly from fuels or other deposits which cannot be mined andv utilized above earth in an economical way.

There are many such deposits that can not be economically mined. Some cannot be so exploited because the deposits have too low a content of combustible matter to be used in that way economically. Others which may contain a satisfactory content of combustible matter, are so situated in the earth, as in depth or thickness of layer, as to make the mining operation unattractive.

Methods of underground combustion have been heretofore proposed but have not been successful because of the difiiculty of distributing the combustion supporting gas such as air, in the rock in such manner as to obtain a substantially uniform combustion zone. The introduction of the combustion supporting gas through a borehole into the rock, does not result in uniform flow of the gas because such flow is usually disturbed by the presence of cracks, laminations, cavities, etc. in the rock. As a result of such non-uniform flow, the combustion zone may advance along a crack in one direction very rapidly to a relatively distant location from the inlet hole, While in the meantime, the advance in another direction may be very slow due to a greater tightness or impermeability or density of the structure. Under such circumstances, it has been impossible by prior art procedures to control the heat distribution to the parts of the rock where the heat treatment is to be applied.

Among the objects of the present invention are included methods for combustion in situ of combustible organic material in subterranean deposits with substantially uniformheat distribution therein despite irregularities in the formation that might otherwise interfere with uniformity of heat distribution.

Other objects include the production of a controlled combustion zone and a controlled heat transfer" to other portions of the rock or formation or deposit.

Further objects and advantages of this invention will appear fromthe more detailed description set forth be low, it being understood that such more detailed description is given by way of illustration and explanation only, and not by way of limitation since various changes therein may be made by those skilled in the art without departing from the scope and spirit of the present invention.

. In connection with that more detailed description, the drawings show the following:

Figure l is a plan view of a field showing a number of boreholes for utilization in connection with the present invention;

Figure 2 is a transverse vertical section through the field of Figure 1;

Figure 3 is an enlarged fragmentary view of a portion.

of the section of Figure 2;

Figure 4 is a section on the line 44 of Figure 3; and Figure 5 is a section on line 4--4 of Figure 3 illustrating the heat front developed by the present invention. The present invention produces combustion in situ of combustible organic material contained in subterranean deposits under controlled conditions to produce a controlled combustion zone and a controlled heat transfer from the combustion zone to other parts of the rock, formation, or deposit. The controlled conditions are obtained by withdrawal of combustion gases from boreholes in the vicinity of the air-inlet boreholes. This withdrawal may be attained for example by suction in the pipelines, connected to the outlet holes. Thereby the hot combustion gases are forced to flow in certain directions and their flow can thus be regulated and controlled. When passing through the outlet holes towards the exit thereof, they give off at least part of their heat'content to the Walls of the borehole, thus raising the temperature of said walls. In said walls the heat is fairly well distribu ted along the length of the hole and thus a' substantially uniform or even heat transfer takes place from saidwalls to the surrounding parts of the rock. 'The invention is applicable to any subterranean deposits of combustible organic material including oil shale and oil shale coke (the latter being formed by in-situ pyrolysis of oil shale), tar sand and tar sand coke (the latter being formed by in-situ pyrolysis of tar sand), oil sand and depleted oil sand, (still retaining a small amount of oil), lignite, coil, or other carbonaceous and combustible or fuel type materials.

For these purposes, any combustion supporting gas such as air or other oxygen containing gas, is introduced to the deposit to produce a combustion zone and to form hot combustion products, the latter are passed through 'the deposit or portion thereof wherethey .are withdrawn, usually in the vicinity of the inlet boreholes for the combustion supporting gases, the heat from said combustion products serving to heat the walls of the outlets and thereby adjacent organic material to form valuable products containing gases or vapors or both. The latter are recovered separately from and substantially free of the combustion products, at a point or points spaced from the point or points where the combustion products are withdrawn; 7

Accordinglymethods of combustion in situ may be utilized wherein deposits pierced by borcholes'in successive alinement serve for introduction respectively of combustion supporting gas, removal of combustion products, and separate removal of valuable products including gases or vapors or both free from combustion products. When the flow of valuable products has ceased or has been reduced to a low value, the borehole which initially served for introduction of the combustion supporting gas is sealed off, the latter gas is then introduced into aborehole used theretofore for collection of combustion products, the combustion products are collected in the borehole theretofore used for reception of the valuable products, and an additional successive alined borehole is then utilized for recovery of the valuable products, the rela tion of heating and heat transfer described above being maintained in the new arrangement. in this Way, the combustion zone may be advanced as desired in the deposit or formation. And by repeating the advance in this way, it is possible to carry out the combustion of the entire or any part of the deposit under controlled conditions advancing through the deposit as desired,

Further features of the invention will appear from the following description thereof in connection with the figures of the drawings,without however any limitation thereto.

Figure 1 is a horizontal drawing of a field, showing a numberofboreholes for the successive use as outlets A for volatilized products, obtained by heat treatment.

of the fuel containing rock layers, outlets B for com- 7 bustion gases; and injection holes C'for air or "other also shows the location of :the abovegmentioned rows of' holes. 7 V I Fig. 3 isan enlargedpart of Fig. 2, showing one'air inlet hole C supplied with air and one combustion-gas outlet hole B which is exhausted. The figure shows how the combustion zone advances'mainly in the fissures and Cavities of the rock. The dotted line G shows the loca-' tion of the combustion zone at a given moment. It is evident that the heat transferv to the surroundings will be very irregular from a hot surface of such an irregular shape. ThecombustionYproducts not being forced to flow in a certain direction, they will spread irregularly in the rock'in the air inlet tube, especially along cracks 1, 2, etc. and fissures in the layers. This irregular flow is shown in Fig. 4, which is a horizontal'section through part of the fuel deposit, on the line 4 -4 in 'Fig. 3. The line'H illustrates the location in this sectionof the combustion zone at a given moment. The irregularity of advance. of the heating'zone is thuslapparent.

If, however, the flow'of combustion gases is directed by applying a lower pressure in the'row of outlet holes B than the pressure in the surrounding rock, the combustion zone will be more regularly 'shaped as shown in Fig. .5; "whichIis a horizontal section, corresponding to Fig.4. .;Even if there. may remain siom e irregularities in the combustion zone, it is evident that, the regular heat'flow in thiscase is much improved compared to that in the case, illustrated in Fig. 4. The essential improve ment in the regular heat flow is, however, created through the regular shape of a hot, cylindrical surface around each outlet'hole B. The hot combustion gases collected in each hole, giveofi part or their heat to the walls of those holes B. If the same subpressure is maintained in the holes B, as in the'product gas outlets 'A,'there is no flow of fluids in direction from A to B or' vice versa.

' Thus thoseparts of the walls of the B -holes, which face the row of A holes, are undisturbed by flows in any cracks etc. .The heat, which is supplied bythe hot combustion gases, arriving from the'opposite side of the holes, and ascending vertically throughtheB-holes, is thus fairly equally distributed along the hole. wall. Thus a hot body is created around the hole, and the part of this hot body, which'faces the row of A-holes, is almost ;cylindrical. The heat transfer by conduction in the rock towards the zone, where the heat is to be utilized (the pyrolysiszone, cracking zone, etc.), will thus be r'egular and'the' shape of'the heat wave, moving forwards through lthe f uel' deposi t, will be that of a surfaceconsisting of a number "of vertical semicylindrical surfaces The heat methods, where heat is supplied through} electrically heated or gas-fired heating. tubes, inserted in drillholes.

product vapors. through the A-holes and the combustion vapors through the B-holes.

actualifie'ld, for instance a triangular,=square. or hexagonal pattern, and tubes whichmaybelinsertediinithe bore holes. The tubes may be perforated in conventional manner along'the part "of the tube which'passesthroug'h shale coke.

the. fuel-containing layers, the purpose of the perforations being to provide a distribution of inlet or outlet fluid through the whole fuel-containingrlayer, or the'y' may be' open in their lower ends and ending at a. certain level, for instance at the top of the fuel deposit. The opentubesmay' be used in deposits that'are consolidated and the whole layer being of approximatelythe same permeability to fluids, I for instance oil shale oil The tubes in the bore-holes pass t ough the overburden and around each tube a packer may be arranged in the overburden in order'to prevent fluids fromescaping from or leaking in tothe fuel deposits between the tube and the borehole. V r

Above ground the tubes are valved and connected to either aircompressors (when the holes are. used for air injection) or fans or blowers (when the holes areTused as gas or vapor outlets). The valves may bemaiiually or automatically operated, to maintain pressures; wanted in the tubes. The vapor outlets in tubes A should further be connected with means fo'r condensation and collection of the obtained air vapors and other products;

Example 7 the Swedish Shale Oil Company, at Kvantorp, "Sweden',

' the hole pattern was a hexagonal one, theedge-lerigth' of annular spacebetween the borehole and th'e tube bein'g the hexagon unit being 2.20 meter. 'I 'he thickness of the V overburden was about S'meter' an'd the thickness of the: V shale coke was'about 15 meters. fThe dianleterfofithe' boreholes was'about 0.060 meter,"and their-depth"was-23 meters thus passing to the bottom of theshale'cokefi' The inserted tubes had a diameter ot about 0.055 fr'neter, the

packed with fine-grained sand. The length-'of=the tube"s was about 9 meters and the lower ends of the tubesfwas located about 0.5 meter below the 'top of the shale'coke layer. through the shalecoke.

When the stated run was performed air 'was blown 7 into three adjacent holes in an amount-ofbetweenf1'00 and 300 m. /hour, totally.- The pressure required'to force the air into the rock was about 150 Hg (gauge). During the air injectiong'temperature measurements were made and gas products weretakenofiat' several points, distributed at difierent distances nqm the injection hole 'group. The shale coke "had fromfi the beginning a temperature offabout300'C; which"was"sufficientffor igniting the coke, when air vvas introduced. 7

(The heat of the coke originated fror n'the earlier electrothermal heating'of this field.) 'The rnovement-of the combustionngasesfin the layers could' be followed 'by means ofgasproductatakezifrom difierent-pointssinthe field. Before the run was. started, 'the' whole shal'e'c'oke layer was filled with gaseous or vaporizedhydrocarbons at a pressure of about lOO mm. Hg'.(. Iemainiflgfronrthe electrothermal pyr'olysis of the shale; This;

' transfer 'conditions may be substantially the same as in v a e -70. The equipment for carrying out the'above-mentionedi combustion, method includes the :boreholesywhichi-may' V 4 inlet hole group. The-faster flow inthis directioifmust. be arrangedfin any regular hole-pattern, coveringthe a crack or other irregularityin the rock pressure was rather equally distributed in the whble'sliale' coke body. .It' was found -that thecombusti'ofi productsspreadin all directions fro rnth e'inlet hole'group; {The velocity of advancement'was about the same in alli direcf tions except in one, in which the combustion gases flow'ed' muchmore rapidly. At a certain moment of 'the'runfthe radius, within which combustionp'roducts were obtained" was about 10-12 meters, in "most directions. *Ifi'fone narrow direction, however, it was found thatthe'comb'us tion gases had moved not less than 27 meters have been due to Below the tube ends the boreholes -were open ucts could be controlled from the surface, the run was repeated with some of the outlet hole valves open to the atmosphere. At these points the pressure in the rock was thus lowered below the pressure of the surroundings (about 100 mm. Hg (gauge)), the run conditions thus being of the same effect as if a suction fan had been connected to outlet points in rock layers, where the original pressure was atmospheric pressure.

In the repeated run it was found that the combustion gases only advanced in the directions towards the open holes. No essential flow in other directions was found to take place, not even in the direction of the crack in the rock.

It was thus found possible to direct the flow of combustion products in desired directions in the rock by means of pressure control on the holes.

In the description of the invention, given above, its usefulness for in-situ-pyrolysis or other heat treatment of shale has been illustrated. The same process of directing the advancement of the combustion zone and of withdrawal of hot combustion gases may also be used as a means of recovery from underground sources of heat for other purposes, for instance for heating of buildings or other structures above ground. The heat of the combustion gases may also be utilized for heat treatment of other underground deposits in the vicinity whereby the hot combustion gases are piped in for example insulated pipes to the actual deposits. Thus the heat value of a shale-coke-containing field may be used for preheating an oil-shale field in another location, or for other purposes.

Having thus set forth my invention, I claim:

1. A method for combustion in situ of combustible organic material in subterranean deposits pierced by inlet and outlet boreholes which comprises introducing a combustion supporting gas through an inlet borehole to said combustible material to produce a combustion zone and to form hot combustion products, passing the products of combustion through the deposit to heat adjacent organic material to form valuable products including gases and vapors, collecting and removing said valuable products including gases and vapors separately from said products of combustion at a first outlet borehole which is located a distance from said combustion zone, collecting and removing the products of combustion separately from the valuable products at a second outlet borehole, said second outlet borehole being located between said first inlet borehole and said first outlet borehole, the pressures at both of said first and second outlet boreholes being below atmospheric and substantially equal; and being lower than pressures at said inlet borehole.

2. A method as set forth in claim 1, which comprises removing said products of combustion from said second outlet borehole while retaining sensible heat to a point above the ground and passing them while retaining substantial sensible heat to a zone adjacent the combustion zone as a source of heat for said combustion zone.

3. A method as set forth in claim 1, wherein a plurality of inlet and outlet boreholes are provided to form a pattern of boreholes, maintaining a pressure differential along a direction between inlet boreholes at which combustion supporting gas is introduced and second outlet boreholes at which combustion gas is Withdrawn thereby causing predirected advancement of the combustion zone along said direction.

4. A method as set forth in claim 3, including the step of flowing combustion gases substantially in one direction towards second outlet boreholes thereby maintaining a substantially uniform heat distribution in said deposit between the inlet borehole for introduction of combustion supporting gas and the first outlet borehole for removal of said valuable products of combustion, said uniform heat distribution being undisturbed by combustion taking place in cracks, fissures and cavities.

5. The method as set forth in claim 3, comprising successively adding an aligned outlet borehole which is in advance of and in aligrunent with said advancing combustion zone for the removal of valuable products free of combustion products While sealing ofi said inlet borehole theretofore used for introduction of combustion supporting gas, introducing the combustion supporting gas to said second outlet borehole theretofo-re used for removal of combustion products and removing combustion products from the first outlet borehole theretofore used for the removal of valuable products, thus advancing the combustion zone for treatment of the deposit.

References (lited in the file of this patent UNITED STATES PATENTS 947,608 Betts Jan. 25, 1910 1,457,479 Wolcott June 5, 1923 2,497,868 Dalin Feb. 21, 1950 FOREEGN PATENTS 123,138 Sweden Nov. 9, 1948 OTHER REFERENCES American Gas Journal, Jan. 1944, pages 28 and 29. 

1. A METHOD FOR COMBUSTION IN SITU OF COMBUSTIBLE ORGANIC MATERIAL IN SUBTERRANEAN DEPOSITS PIERCED BY INLET AND OUTLET BOREHOLES WHICH COMPRISES INTRODUCING A COMBUSTION SUPPORTING GAS THROUGH AN INLET BOREHOLE TO SAID COMBUSTIBLE MATERIAL TO PRODUCE A COMBUSTION ZONE AND TO FORM HOT COMBUSTION PRODUCTS, PASSING THE PRODUCTS OF COMBUSTION THROUGH THE DEPOSIT TO HEAT ADJACENT ORGANIC MATERIAL TO FORM VALUABLE PRODUCTS INCLUDING GASES AND VAPORS, COLLECTING AND REMOVING SAID VALUABLE PRODUCTS INCLUDING GASES AND VAPORS SEPARATELY FROM SAID PRODUCTS OF COMBUSTION AT A FIRST OUTLET BOREHOLE WHICH IS LOCATED A DISTANCE FROM SAID COMBUSTION ZONE, COLLECTING AND REMOVING THE PRODUCTS OF COMBUSTION SEPARATELY FROM THE VALUABLE PRODUCTS AT A SECOND OUTLET BOREHOLE SAID SECOND OUTLET BOREHOLE BEING LOCATED BETWEEN SAID FIRST INLET BOREHOLE AND SAID FIRST OUTLET BOREHOLE, THE PRESSURES AT BOTH OF SAID FIRST AND SECOND OUTLET BOREHOLES BEING BELOW ATMOSPHERIC AND SUBSTANTIALLY EQUAL, AND BEING LOWER THAN PRESSURES AT SAID INLET BOREHOLE. 